In wireless router networks several wireless routers are provided that are connected with radio links in order to establish data communication from a user personal computer (PC) or local area network (LAN) to other larger networks, e.g. to the Internet. Such wireless routers are usually located on the roof of a building or the like and thus remotely located from any electrical or electronic equipment, in particular from any indoor mains power supply. Thus, power has to be fed from a separate power supply unit to the router via a special power line.
In such wireless router networks the wireless router may be embodied as a rooftop subscriber unit (SU) or airhead unit (AH). Such SU or AH is located maximally at a 50-meter distance from an interface and power supply unit. Such an interface and power supply unit is regularly further cabled to a user PC interface. To avoid the use of a separate power supply on the roof of the building, the SU or AH receives its power from the interface and power supply unit which in turn receives power from an indoor mains power supply, which is located near the interface and power supply unit. The power is fed to the SU or AH through the same cable carrying the data between the SU/AH and the interface and power supply unit. The data transmission method for the transmission of this data is either an 10/100 Ethernet or a Home PNA (Phoneline Networking Alliance) connection.
In addition to corresponding Ethernet or Home PNA interfaces the SU/AH needs extra interfaces to receive power from the interface and power supply unit. Furthermore, a user and service personnel frequently needs extra information about the status of the SU/AH and auxiliary functional user and maintenance data. For this purpose the interface and power supply unit is commonly equipped with some light emitting diodes (LEDs) to indicate the basic functionality of the router, like power on/off, ongoing data traffic, and diagnostic information. This additional information has to be transmitted from the SU/AH to the user and hence to the interface and power supply unit. Typically this requires additional interfaces in both units and additional wires in the data communication cable.
Commonly any extra data transferred between the SU/AH and the interface and power supply unit has been using a parallel interface and a separate wire for every bit of information. This is a very straight forward implementation but it requires extra wires in the data communication cable. Furthermore, all interfaces in both ends of the cable have to be protected against energetic surges, which considerably increases the costs and complexity of the otherwise simple and inexpensive interface circuitry.
Data communication cables readily available on electronics retail markets suitable for Ethernet links contain maximally four twisted pairs. However, at the present, the SU/AH requires a cable with seven pairs to carry the data, power, and auxiliary indicator data from the SU/AH to the interface and power supply unit. This requirement leads to a customized cable, which is not readily available and must therefore always be delivered with the router. Using such a customized cable with extra pairs increases costs considerably.
Furthermore, the assembly conditions vary and the length of the cable cannot easily be estimated before the actual assembly work. This leads to the need of purchasing excessive cable lengths, which further increases costs.
Furthermore, cable conduits are often so narrow that a ready-made cable with a connector pre-assembled to the customized cable cannot be pulled through the cable conduit. This may lead in some cases to the requirement of assembling a connector on the roof, which may be difficult due to the required special tools and in some cases due to adverse weather and difficult working conditions.
The ideal case would be that the cable can be purchased locally, assembled quickly and cut to the desired length at both ends with no special tools with minimal numbers of connections to be made on the installation site.
The above mentioned drawbacks may also occur in other areas with similar remotely located devices utilising centralised power feed systems through data communication cables.